kern/54486: athn driver panics on arm

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         54486
>Category:       kern
>Synopsis:       athn driver panics on arm
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Aug 23 15:00:00 +0000 2019
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date 2019.08.23.07.29.29
>Organization:

>Environment:
System: NetBSD
Architecture: earmv7hf
Machine: evbarm
>Description:

Booting NetBSD-current on a Raspberry Pi 3 model B with a Comfast
CF-WU871N WiFi adapter plugged into a USB port, the kernel panics
with an "Alignment Fault 1" in athn_usb_start.  Attach message:

  http://www.gson.org/netbsd/bugs/athn.arm/attach.jpg

Panic message and backtrace:

  http://www.gson.org/netbsd/bugs/athn.arm/panic.jpg

This is the same adapter as in PRs 51151 and 52526.

>How-To-Repeat:

>Fix: